21-norvitamin D compounds

ABSTRACT

21-norvitamin D 3  analogs in which the methyl group normally attached to the side chain at carbon 20 has been replaced by a hydrogen atom. The compounds are characterized by a marked intestinal calcium transport activity while exhibiting much lower activity than 1α,25-dihydroxyvitamin D 3  in their ability to mobilize calcium from bone. Because of their preferential calcemic activity, these compounds are useful for the treatment of diseases where bone formation is desired, such as osteodystrophy. Novel intermediates formed during the synthesis of the end products are also disclosed.

This invention was made with United States Government support awarded bythe National Institutes of Health (NIH), Grant No. DK-14881. The UnitedStates Government has certain rights in this invention.

BACKGROUND OF THE INVENTION

This invention relates to biologically active vitamin D compounds. Morespecifically, the invention relates to 21-norvitamin D compounds, to ageneral process for their preparation, and to their use in treatingosteoporosis.

With the discovery of 1α,25-dihydroxyvitamin D₃ as the active form ofthe vitamin has come an intense investigation of analogs of thishormonal form of vitamin D with the intent of finding analogs that haveselective activity. By now, several compounds have been discovered whichcarry out the differentiative role of 1,25-dihydroxyvitamin D₂ whilehaving little or no calcium activity. Additionally, other compounds havebeen found that have minimal activities in the mobilization of calciumfrom bone while having significant activities in stimulating intestinalcalcium transport. Modification of the vitamin D side chain bylengthening it at the 24-carbon has resulted in loss of calcium activityand either an enhancement or undisturbed differentiative activity.Placing the 24-methyl of 1α,25-dihydroxyvitamin D₂ in theepi-configuration appears to diminish activity in the mobilization ofcalcium from bone. On the other hand, increased hydrophobicity on the26--and 27--carbons seems to increase the total activity of the vitaminD compounds provided the 25-hydroxyl is present.

Several of these known compounds exhibit highly potent activity in vivoor in vitro, and possess advantageous activity profiles and thus are inuse, or have been proposed for use, in the treatment of a variety ofdiseases such as renal osteodystrophy, vitamin D-resistant rickets,osteoporosis. psoriasis, and certain malignancies.

It is well known that females at the time of menopause suffer a markedloss of bone mass giving rise ultimately to osteopenia, which in turngives rise to spontaneous crush fractures of the vertebrae and fracturesof the long bones. This disease is generally known as postmenopausalosteoporosis and presents a major medical problem, both in the UnitedStates and most other countries where the life-span of females reachesages of at least 60 and 70 years. Generally, the disease which is oftenaccompanied by bone pain and decreased physical activity, is diagnosedby one or two vertebral crush fractures with evidence of diminished bonemass. It is known that this disease is accompanied by diminished abilityto absorb calcium, decreased levels of sex hormones, especially estrogenand androgen, and a negative calcium balance.

Similar symptoms of bone loss characterize senile osteoporosis andsteroid-induced osteoporosis, the latter being a recognized result oflong term glucocorticoid (cortico-steroid) therapy for certain diseasestates.

Methods for treating the disease have varied considerably but to date nototally satisfactory treatment is yet known. A conventional treatment isto administer a calcium supplement to the patient. However, calciumsupplementation by itself has not been successful in preventing orcuring the disease. Another conventional treatment is the injection ofsex hormones, especially estrogen, which has been reported to beeffective in preventing the rapid loss of bone mass experienced inpostmenopausal women. This technique, however, has been complicated bythe fact of its possible carcinogenicity. Other treatments for whichvariable results have been reported, have included a combination ofvitamin D in large doses, calcium and fluoride. The primary problem withthis approach is that fluoride induces structurally unsound bone, calledwoven bone, and in addition, produces a number of side effects such asincreased incidence of fractures and gastrointestinal reaction to thelarge amounts of fluoride administered. Another suggested method is toblock bone resorption by injecting calcitonin or providing phosphonates.

U.S. Pat. No. 4,225,596 suggests the use of various metabolites ofvitamin D₃ for increasing calcium absorption and retention within thebody of mammals displaying evidence of or having a physiologicaltendency toward loss of bone mass. The metabolites specifically named inthat patent, i.e., 1α-hydroxyvitamin D₃, 1α-hydroxyvitamin D₂1α,25-dihydroxyvitamin D₃,1α,25-dihydroxyvitamin D₂ and1,24,25-trihydroxyvitamin D₃, although capable of the activity describedand claimed in that patent are also characterized by the disadvantage ofcausing hypercalcemia especially if used with the conventional calciumsupplement treatment. Therefore, use of these compounds to treatosteoporosis has not been widely accepted. U.S. Pat. Nos. 3,833,622 and3,901,928 respectively suggest using the hydrate of 25-hydroxyvitamin D₃and 1α-hydroxyvitamin D₃ for treatment of osteoporosis in a generalexpression of utility for those compounds. It is well known both ofthose compounds express traditional vitamin D-like activity, includingthe danger of hypercalcemia.

U.S. Pat. No. 4,588,716 also suggests the use of 1α,25-dihydroxy-24-epi-vitamin D₂ to treat bone disorders characterized bythe loss of bone mass, such as osteoporosis. This compound expressessome of the vitamin D-like characteristics affecting calcium metabolismsuch as increasing intestinal calcium transport and stimulating themineralization of new bone. It has the advantage of minimaleffectiveness in mobilizing calcium from bone. The 24-epi compound maybe administered alone or in combination with a bone mobilizationinducing compound such as a hormone or vitamin D compound such as1α-hydroxyvitamin D₃ or D₂ or 1α,25-dihydroxyvitamin D₃ or D₂.

U.S. Pat. No. 5,194,431 discloses the use of 24-cyclopropane vitamin D₂compounds in treating osteoporosis. Also, U.S. Pat. No. 4,851,401discloses the use of cyclopentano 1,25-dihydroxyvitamin D₃ compounds inthe treatment of osteoporosis and related diseases.

In an ongoing effort to develop a treatment for osteoporosis, the carbon20 position of the side-chain was investigated to determine itspotential. Altering the order of substituents or the substitutionpattern on carbon 20 could result in a change of minimum energy positionfor conformations around the C₁₇ -C₂₀ bond, and consequently, in achange of side-chain orientation with respect to the ring system.Orientation of the side-chain with respect to the ring system andconfiguration on the C₂₀ may have important consequences for biologicalproperties of cholestane derivatives, in particular vitamin D compounds.It is well documented that binding of 1α,25-dihydroxyvitamin D₃ (1,Scheme 1) involves active centers in the ring A and triene system aswell as in the side-chain. Altering the "normal configuration" around C₇-C₂₀ bond in vitamin D could change the distance between active centerswithin the molecule, and thus result in a change in activity of suchcompounds.

A synthesis of 1α,25-dihydroxy-21 -norvitamin D₃ was described inKuboderal et al, "Synthetic Studies of Vitamin D Analogs. X. Synthesisand Biological Activities of 1α,25-Dihydroxy-21-Norvitamin D₃ ", Chem.Pharm. Bull., 40(3) 648-651 (1992) from1α-hydroxydehydroepiandrosterone. Certain biological properties of1α,25-dihydroxy-21-norvitamin D₃ were also examined and compared withthose of 1α,25-dihydroxyvitamin D₃ and1α,25-dihydroxy-21-nor-20-oxavitamin D₃ to evaluate the effect of the21-methyl substituent on biological properties.

SUMMARY OF THE INVENTION

The present invention provides a novel treatment of metabolic bonediseases which utilizes 21-norvitamin D compounds exhibiting a desired,and highly advantageous, pattern of biological activity. These compoundsare characterized by a marked intestinal calcium transport activity, ascompared to that of 1α,25-dihydroxyvitamin D₃, while exhibiting muchlower activity than 1α,25-dihydroxyvitamin D₃ in their ability tomobilize calcium from bone. Hence, these compounds are highly specificin their calcemic activity. Their preferential activity on intestinalcalcium transport and reduced calcium mobilizing activity in bone allowsthe in vivo administration of these compounds for the treatment ofmetabolic bone diseases where bone loss is a major concern. Because oftheir preferential calcemic activity, these compounds would be preferredtherapeutic agents for the treatment of diseases where bone formation isdesired, such as osteoporosis, osteomalacia and renal osteodystrophy.

Structurally, the key feature of the compounds having these desirablebiological attributes is that they are analogs of 1,25-dihydroxyvitaminD₃ in which the methyl group normally attached to the side-chain atcarbon 20 has been replaced by a hydrogen atom. Thus, the compounds ofthis type are characterized by the following general structure: ##STR1##where X₁ may be hydrogen or a hydroxy-protecting group, X₂ may behydrogen, hydroxy, or protected hydroxy, and where Z is selected fromthe group consisting of Y, --OY, --CH₂ OY, --C.tbd.CY and --CH═CHY,where the double bond may have the cis or trans stereochemicalconfiguration, and where Y is selected from the group consisting ofhydrogen, methyl, --CR₅ O and a radical of the structure ##STR2## wherem and n, independently, represent the integers from 0 to 5, where R¹ isselected from the group consisting of hydrogen, hydroxy,protected-hydroxy, fluoro, trifluoromethyl, and C₁₋₅ -alkyl, which maybe straight chain or branched and, optionally, bear a hydroxy orprotected-hydroxy substituent, and where each of R², R³ and R⁴,independently, is selected from the group consisting of hydrogen,fluoro, trifluoromethyl and C₁₋₅ alkyl, which may be straight-chain orbranched, and optionally bear a hydroxy or protected-hydroxysubstituent, and where R¹ and R², taken together, represent an oxogroup, or an alkylidene group, ═CR₂ R₃, or the group --(CH₂)_(p) --,where p is an integer from 2 to 5, and where R³ and R⁴, taken together,represent an oxo group, or the group --(CH₂)_(q) --, where 9 is aninteger from 2 to 5, and where R⁵ represents hydrogen, hydroxy,protected-hydroxy, or C₁₋₅ alkyl.

The present invention, therefore, provides 21-norvitamin D compoundsshowing preferential activity on intestinal calcium transport andreduced calcium mobilizing activity in bone, and are useful for thetreatment of metabolic bone disease, such as osteoporosis, where boneloss is a major concern. More specifically, the preferred compound to beadministered is 1α,25-dihydroxy-21-norvitamin D₃.

This invention also provides novel intermediate compounds formed duringthe synthesis of the end products. Structurally, the intermediatecompounds are characterized by the following general structure: ##STR3##where X₃ may be hydrogen or a hydroxy-protecting group, and Z is aspreviously defined herein.

Other key intermediates are characterized by the following generalstructure: ##STR4## where X₄ and X₅ which may be the same or different,is hydrogen, hydroxy, or oxygen, and Z is as previously defined herein.

Still other key intermediates are 21-norvitamin D₃ compounds which arecharacterized by the following general structure: ##STR5## where X₆ maybe hydrogen or a hydroxy-protecting group, and Z is as previouslydefined herein. In particular, 25-hydroxy-21-norvitamin D₃ is disclosed.

It has now been found that the loss of bone mass, which ischaracteristic of osteoporosis may be effectively treated by theadministration of a 21-norvitamin D compound in sufficient amounts toincrease bone mass. More specifically, a method of treating osteoporosiscomprises the administration of an effective amount of a 21-norvitamin Dcompound, preferably 1α,25-dihydroxy21-norvitamin D₃. The abovecompounds may be administered alone or in combination with otherpharmaceutically acceptable agents. Dosages of from not less than about0.5 μg/day to not more than about 50 μg/day of the individual compoundper se, or in combinations, are generally effective. This method has thedistinct advantage that it will restore bone mass due to theinsignificant bone mobilization activity of these compounds and furtherthese compounds advantageously will not cause hypercalcemia even if thecompound is administered continuously on a daily basis, as long as theappropriate compound dosages are used, it being understood that thedosage levels will be adjusted dependent on the response of the subjectas monitored by methods known to those skilled in the art.

The above method, involving the administration of the indicated dosagesof 21-norvitamin D compounds such as 1α,25-dihydroxy-21-norvitamin D₃ iseffective in restoring or maintaining bone mass, and thus provides anovel method for the treatment or prevention of various forms ofosteoporosis such as postmenopausal osteoporosis, senile osteoporosisand steroid-induced osteoporosis. It will be evident that the methodwill find ready application for the prevention or treatment of diseasestates other than those named, such as renal osteodystrophy.

DETAILED DESCRIPTION OF THE INVENTION

As used in the description and in the claims, the termhydroxy-protecting group signifies any group commonly used for thetemporary protection of hydroxy functions, such as for example,alkoxycarbonyl, acyl, alkylsilyl, and alkoxyalkyl groups, and aprotected hydroxy group is a hydroxy function derivatized by such aprotecting group. Alkoxycarbonyl protecting groups are groupings such asmethoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl,butoxycarbonyl, ixobutoxycarbonyl, tert-butoxycarbonyl,benzyloxycarbonyl or allyloxycarbonyl. The term `acyl` signifies analkanoyl group of 1 to 6 carbons, in all of its isomeric forms, or acarboxyalkanoyl group of 1 to 6 carbons, such as an oxalyl, amlonyl,succinyl, glutaryl group, or a aromatic acyl group such as benzoyl, or ahalo, nitro or alkyl substituted benzoyl group. The word `alkyl` as usedin the description or the claims, denotes a straight-chain or branchedalkyl radical of 1 to 10 carbons, in all its isomeric forms. Alkoxyalkylprotecting groups are groupings such as methoxymethyl, ethoxyethyl,methoxyethoxymethyl, or tetrahydrofuranyl and tetrahydropyranyl.Preferred alkylsilyl protecting groups are trimethylsilyl,triethylsilyl, t-butyldimethylsilyl, and analogous alkylated silylradicals.

The vitamin D compounds useful in the present treatment are21-norvitamin D compounds, preferably 1α,25-dihydroxy-21-norvitamin D₃.The above compounds may be administered alone or in combination withother pharmaceutically acceptable agents.

The 21-norvitamin D compounds or combinations thereof can be readilyadministered as sterile parenteral solutions by injection orintravenously, or by alimentary canal in the form of oral dosages, ortransdermally, or by suppository. Doses of from about 0.5 micrograms toabout 50 micrograms per day of the compounds per se, or in combinationwith other 1α-hydroxylated vitamin D compounds, the proportions of eachof the compounds in the combination being dependent upon the particulardisease state being addressed and the degree of bone mineralizationand/or bone mobilization desired, are generally effective to practicethe present invention. In all cases sufficient amounts of the compoundshould be used to restore bone mass. Amounts in excess of about 50micrograms per day or the combination of that compound with other1α-hydroxylated vitamin D compounds, are generally unnecessary toachieve the desired results, may result in hypercalcemia, and may not bean economically sound practice. In practice the higher doses are usedwhere therapeutic treatment of a disease state is the desired end whilethe lower doses are generally used for prophylactic purposes, it beingunderstood that the specific dosage administered in any given case willbe adjusted in accordance with the specific compounds beingadministered, the disease to be treated, the condition of the subjectand the other relevant medical facts that may modify the activity of thedrug or the response of the subject, as is well known by those skilledin the art. For example, to be effective, the1α,25-dihydroxy-21-norvitamin D₃ compound is preferably administered ina dosage range of 0.5-50 μg/day. In general, either a single daily doseor divided daily dosages may be employed, as is well known in the art.

Dosage forms of the various compounds can be prepared by combining themwith non-toxic pharmaceutically acceptable carriers to make eitherimmediate release or slow release formulations, as is well known in theart. Such carriers may be either solid or liquid such as, for example,corn starch, lactose, sucrose, peanut oil, olive oil, sesame oil andpropylene glycol. If a solid carrier is used the dosage form of thecompounds may be tablets, capsules, powders, trochees or lozenges. If aliquid carrier is used, soft gelatin capsules, or syrup or liquidsuspensions, emulsions or solutions may be the dosage form. The dosageforms may also contain adjuvants, such as preserving, stabilizing,wetting or emulsifying agents, solution promoters, etc. They may alsocontain other therapeutically valuable substances.

The present invention is more specifically described by the followingexamples, which are meant to be illustrative only of the process ofsynthesis and of the novel compounds, both end products andintermediates, obtainable thereby. In these examples, specific compoundsidentified by Arabic numerals (e.g. compounds 1, 2, 3, . . . etc.) referto the structures so numbered in the process schematics. Additionallyexamples are provided which are illustrative of the distinctivebiological characteristics of the new compounds, such characteristicsserving as a basis for the application of these compounds in thetreatment of metabolic bone disease.

Chemistry

The synthetic route to 1α,25-dihydroxy 21-norvitamin D₃ 2a, whichincludes 25-hydroxy-21-norcholesterol acetate 9a, 21-norvitamin D₃ 11aand 3,5-cyclo-9,10-seco-derivatives 12a, 12b as key intermediates waschosen.

For synthesis of the 5-hydroxy-21-norcholesterol 9 methodology developedfor the early synthesis of 25-hydroxycholesterol was explored. Uskovicet al, Helv. Chim. Acta, 1974. 57:768; Wicha et al, Synth. Comm., 1977,7:215-222; and Wicha et al, J. Chem. Soc., Perkin 1, 1978, 1282. Thus,readily available androstane derivative 4 was subjected to reaction withan anion generated from triethylphosphonoacetate and the condensationproduct 5a was transformed to the i-steroid 6a via tosylate 5b.Noteworthy, during methanolysis of tosylate 5b under Butenandt andGrosse conditions, Butenandt et al, Chem. Ber., 1936, 69:2777, noexchange of the ester ethyl for methyl group occurred. Reduction of theester group in 6a with hydride afforded allylic alcohol 6b which onhydrogenation gave the saturated derivative 7a. The respective tosylate,7b, was coupled with lithium derivative of 3-methyl-1-butyn-3-yl2-tetrahydropyranyl ether Barton et al, J. Chem. Soc., (c), 1970, 1584,accordingly to the procedure of Uskokovic, et al, Helv. Chim Acta, 1973,57:758, to give the 21-nor-23-yn cholestane derivative 8a which washydrogenated over palladium catalyst. The product of hydrogenation, 8b,was subjected to solvolysis in glacial acetic acid to give required25-hydroxycholesterol acetate 9b in 36% overall yield from starting17-oxoandrostane 4 (9 steps). Alternatively, i-steroid 8b was treatedwith p-toluenesulphonic acid (PTSA) in aqueous dioxane to give describedPumar et al, An. Quim., Ser. C, 1988, 84:105-111,25-hydroxy-21-norcholesterol 9a which was acetylated to give 9b.

Conventional bromination-dehydrobromination of compound 9b followed bytreatment of the crude product with PTSA in dioxane and chromatographyon a silica gel column Uskokovic et al, J. Org. Chem., 1981, 46: 1030,afforded pure acetoxy diene 10b in a 39% yield. The respective alcohol10a was subjected to photolysis using medium-pressure UV lamp equippedwith Vycor filter. The reaction was monitored with HPLC and was stoppedat the ca. 50% of conversion of the starting diene. The crude productwas heated in ethanol at 75° C. for 6 hours and then chromatographed togive triene 11a (at least 90% pure, accordingly to ¹ H NMR) in a 24%yield.

Homoallylic alcohol 11a was treated with tosyl chloride in pyridine togive rosylate 11b. Methanolysis, M. Sheves et al J. Am. Chem. Soc.,1975, 97:6249, of tosylate 8b afforded the cyclopropane derivative 12awhich was purified by chromatography. This key intermediate (12a) washydroxylated, Paaren et al, J. Org. Chem, 1980, 45:3253; DeLuca et al,U.S. Pat. No. 4,555,364, to give 1α-hydroxy derivative 12b accompaniedby small amount of α,β-ketone 12c which easily removed bychromatography. Solvolysis of methoxy cyclopropane 12b in acetic acidafforded acetoxy triene 2b as a mixture of 5Z and 5E isomers in a 2:1ratio (HPLC, ¹ H NMR). Unrequired E isomer was removed by virtue of itsfacile reaction with maleic anhydride, DeLuca et al, U.S. Pat. No.4,555,364. Finally, the ester group in 2b was saponified and1α,25-dihydroxy-21-norvitamin D₃ 2a was purified by columnchromatography.

Experimental

Melting points were determined on a Thomas Hoover capillary meltingpoint apparatus and are uncorrected. Spectra were recorded using thefollowing instruments: ¹ H NMR-Brucker AM 400 or AM 500, as indicated(for deuteriumchloroform solutions with tetramethylsilane as an integralstandard), UV-Perkin-Elmer Lambda 3B uv/vis (for ethanol solutions),mass and high resolution mass-Kartos MS-50Ts (70 eV). All reactionsinvolving dienes or trienes were carried out under argon. Organicsolutions were dried over anhydrous sodium sulfate and solvents wereevaporated on a rotary evaporator. Column chromatography was performedusing silica gel, Merck, 60, 230-400 mesh and preparative layerchromatography (PLC) using precoated silica gel plates, 20×20×0.025 cm,Merck. For high pressure liquid chromatography (HPLC) Waters Associated6VK instrument equipped with Zorbax silics column (6.2 mm×20 cm) wasused.

Ethyl 6β-methoxy-3α,5-cyclo-5α-pregn-5,17(20) (E)-en-21-oate (6a)

A mixture of ethyl 3b-hydroxypregna-5,17(20) (E)-dien-21-oate (5a) (14.3g, 0.04 mol), Wicha et al, Synth. Comm., 1977, 7:215-222, tosyl chloride(9.5 g, 0.05 mol) and pyridine (50 ml) was stirred at room temperaturefor 4.5 hours and then it was filtered and poured into ice-cold 10%aqueous HCl (500 ml). The product was extracted with ether (3×100 ml).Usual workup of the extract afforded an oil which was crystallized frommethylene chloride-hexane to give tosylate 5b

m.p. 122°-124° C. (17.7 g, 86% yield).

A mixture of Tosylate 5b (17.4 g, 0.034 mol), potassium acetate (33.3 g,0.34 mol) and anhydrous methanol (600 ml) was heated under reflux for 4hours. Bulk of methanol was evaporated in vacuo, the residue was takenup in ether (100 ml) and water (100 ml), the layers were separated andthe aqueous layer was extracted with ether (100 and 50 ml). Combinedorganic extracts were washed with water and then with brine. The solventwas evaporated and the residue was dried in high vacuum to give 6a (12.6g, 100% yield).

¹ H NMR(500) δ (ppm) 5.53(1H, t, J=2 Hz, C₂₀ --H), 4.2-4.1(2H, m, 12lines, OCH₂ CH₃), 3.34(3H, s, OCH₃), 2.85-2.75(3H, m, C₆ -and allylicH), 1.28(3H, t, J=6.6 Hz, OCH₂ CH₃), 1.04(3H, s, C₁₉ -H), 0.87(3H, s,C₁₈ -H), 0.67(1H, dd, J₁ =J₂ =4.3 Hz) and 0.46(1H, dd, J₁ =8.0, J₂ =5.3Hz, cyclopropane H). High resolution mass spec. for C₂₄ H₃₆ O₃ calcd.:372.2663(M⁺); found: 372.2664; 357.2430(M⁺ --CH₃, 24%), 341.2459(M⁺--CH₃ OH, 7%) 317.2 123(M⁺ --C₄ H₉, 39%).

This product was contaminated with ca. 10% of the corresponding3-methoxy-5-ene derivative, ¹ H NMR δ 5.38 (m, C₂₀ -H), 3.50(m, C₃ -H),3.35(s. OCH₃) and with small mount of the starting alcohol (5a, lessthan 5%).

21-Hydroxy-6β-methoxy-3α,5-cyclo-5α-pregn-17,20 (E)-ene (6b)

A mixture of ester 6a (3.6 g), lithiumaluminum hydride (1.0 g) and ether(30 ml) was heated under reflux for 1 h. The reagent excess wasdecomposed with saturated aqueous Na₂ SO₄ and the product was isolatedin the usual way. Alcohol 6b was obtained (3.12 g, 99% yield) ascolorless oil; a sample was purified by PLC (hexane-ethyl acetate, 3:2,2 developments);

¹ H NMR (500) δ5.27-5.20(1H, m, C₂₀ --H), 4.14(1H, dd, J_(21a),21b =12,J_(21a),20 =7 Hz, C_(21a) --H), 4.10(1H, dd, J_(21b),21a =12, J_(21b),20=6 Hz, C_(21b) --H), 3.34(3H, s, OCH₃), 2.80(1H, br s, C₆ --H), 1.05(3H,s, C₁₉ --H), 0.82(3H, s, C₁₈ --H), 0.67(1H, dd, J₁ =J₂ =4.3 Hz) and0.45(1H, dd, J₁ =8.0, J₂ =5.3 Hz, cyclopropane H). High resolution massspec. for C₂₂ H₃₄ O₂ calcd.: 330.2560(M⁺); found: 330.2595; 315.2329(M⁺--CH₃, 11%), 299.2382(M⁺ --CH₃ OH, 21%), 275.2012(M⁺ --C₄ H₉, 100%).

¹ H NMR in agreement with that described. Kurek-Tyrlik et al, J. Org.Chem., 1990, 55:3484.

21-Hydroxy-6β-methoxy-3α,5-cyclo-5α-pregnane (7a)

A solution of unsaturated alcohol 6b (1.94 g) in ethanol (30 ml)containing platinium oxide (0.1 g) was stirred under hydrogen for 6 h.Usual workup of the reaction mixture gave saturated alcohol 7a (1.86 g,96% yield). A sample was purified by PLC (hexane-ethyl acetate, 4:1, 4developments), m.p. 87°-89° C. (hexane), ¹ H NMR (500) δ 3.75-3.62(1H,m, C₂₁ -Ha), 3.61(1H, dt, J_(21b),21a =10.4. J_(21b),20 =7.0 Hz, C₂₁-Hb), 3.33(3H, s, OCH₃), 2.77(1H, br s, C₆ --H), 1.03(3H, s, C₁₉ --H),0.65(3H, s, C₁₈ --H) overlapping 0.67(1H, m, cyclopropane H), 0.44(1H,dd, J₁ =7.9, J₂ =5.2 Hz, cyclopropane H). High resolution mass spec. forC₂₂ H₃₆ O₂ calcd.: 332.2716(M⁺); found: 332.2715; 317.2469(M⁺ --CH₃,69%), 300.2475(M⁺ --CH₃ OH, 97%), 277.2172(M⁺ --C₄ H₉, 100%).

6β-Methoxy-21-tosyloxy-3α,5-cyclo-5α-pregnane (7b)

A procedure described for preparation of a similar compound was used.Uskokovic et al, Helv. Chim. Acta, 1974, 57:768.

To a stirred solution of alcohol 7a (1.71 g, 5.14 mmol) in anhydrouspyridine (2 ml) a solution of tosyl chloride (1.24 g, 6.52 mmol) inpyridine (2 ml) was added at 0° C. The mixture was stirred at 0° C. for3 h and then a few chips of ice were added. After 5 min the mixture waspoured into ice and water and the product was extracted with methylenechloride (20 and 2×15 ml). The extract was washed consecutively with 5%HCl, water, saturated aqueous NaHCO₃ and brine. Evaporation of thesolvent gave tosylate 7b (2.43 g, 97% yield) as a crystalline mass; onerecrystallization from methylene chloride-hexane gave product m.p.110°-111° C. A sample was purified by PLC (hexane-ethyl acetate, 3:1

¹ H NMR (500 δ 7.79(2H, d, J=8.2 Hz) and 7.35(2H, d, J=8.1 Hz, aromaticH) 4.08-4.03(1H, m, C₂₁ -Ha), 4.00(1H, dt, J_(21b),21a =9.6, J_(21b),20=7.0 Hz, C₂₁ --Hb), 3.32(3H, s, OCH₃), 2.76(1H, br s, C₆ --H), 2.45(3H,s, C₆ H₄ CH₃), 1.02(3H, s, C₁₉ --H), 0.65(1H, t, J=4.6 Hz, cyclopropaneH), 0.58(3H, s, C₁₈ --H), 0.43(1H, dd, J₁ =7.9, J₂ =5.2 Hz, cyclopropaneH). High resolution mass spec. for C₂₉ H₄₂ O₄ S calcd.: 486.2824 (M⁺);found: 486.2804(26%); 471.2591 (M⁺ --CH₃, 26%), 454.2400(M⁺ --CH₃ OH,100%), 431.2214(M⁺ --C₄ H₉, 44%).

6β-Methoxy-25-(tetrahydropyranyl-2-oxy)-3α,5-cyclo-21-nor-5α-cholest-23-yne (8a)

To a stirred under argon solution of 3-methyl-1-butyn-3-yl2-tetrahydropyranyl ether (2.3 g, 23.7 mmol), Barton et al J. Chem. Soc,(c), 1970, 1584, in anhydrous dioxane (25 ml) n-butyllithium (1.6M inhexane, 9 ml, 14.4 mmol) was added at 5° C. The mixture was stirred at5° C. for 1.5 h and then at the room temperature for 1.5 h whereupontosylate 7b (1.80 g, 3.7 mmol) in dioxane (20 ml) was added and themixture was heated under reflux for 72 h. After cooling, the mixture waspoured into water containing an excess of ammonium chloride and theproduct was extracted with ethyl acetate. The extract was washed withwater and with brine. The solvent was evaporated and the residue wasdried in high vacuum for 16 h to give the crude product 8a (2.98 g). Asample was purified by PLC (hexane-ethyl acetate, 4:1);

¹ H NMR (500) δ 5.05-5.03(1H, m, THP acetal H), 3.95-3.90(1H, m) and3.50-3.45(1H, m, THP-H), 3.33(3H, s, OCH₃), 2.77(1H, br s, C₆ --H),2.28-2.20(1H, m, 8 line, C_(22a) --H), 2.12 and 2.13(1H, 2dt, J₂₂,22a=16.6, J_(22b),20 =7.9 Hz, C_(22b) --H), 1.50 and 1.46(6H, 2s, C₂₆ --and C₂₇ --H) 1.03(3H, s, C₁₉ --H), 0.64(3H, s, C₁₈ --H) overlapping0.66-0.64(1H, m, cyclopropane H). 0.4379(1H, dd, J₁ =8, J₂ =5.1 Hz,cyclopropane H). High resolution mass spec. for C₃₂ H₅₀ O₃ calcd.:482.3760(M⁺); found: 482.3755.

6β-Methoxy-25-(tetrahydropyranyl-2-oxy)-3α,5-cyclo-21-nor -5α-cholestane(8b)

A mixture of the crude product 8a (2.78 g), 5% palladium on activatedcarbon (0.15 g), NaHCO₃ (0.60 g) and dioxane (20 ml) was stirred underhydrogen for 24 h. The solid was filtered off and the filtrate wasevaporated to give the saturated derivative 8b (2.98 g). A sample waspurified by PLC (hexane-ethyl acetate, 4:1).

¹ H NMR (500) δ 4.71(1H, br d, J=5.8 Hz, THP acetal H), 4.00-3.95(1H, m)and 3.50-3.45(1H, m, THP-H), 3.33(3H, s, OCH₃), 2.77(1H, br s, C₆ --H),1.20 and 1.19(6H, 2s, C₂₆ -- and C₂₇ --H) 1.01(3H, s, C₁₉ --H),0.66-0.64(1H, m, cyclopropane H), 0.64(3H, s, C₁₈ --H), 0.43(1H, dd, J₁=8, J₂ =5.1 Hz, cyclopropane H). High resolution mass spec. for C₃₂ H₅₄O₃ calcd.: 486.4073(M⁺); found: 486.4065.

25-Hydroxy-21-norcholesterol (9a)

A solution of 3,5-cyclo-derivative 8b (0.19 g) in 50% aqueous dioxane (6ml) containing p-toluenesulphonic acid (3 mg) was stirred at 80° C. for6 h. The mixture was diluted with water and extracted with chloroform.Usual workup of the extract afforded crude diol 9a (0.13 g) which wascrystallized from methanol to give TLC pure material (0.07 g).Chromatography of the mother liquors on silica gel (3 g, hexane-ethylacetate, 4:1) afforded additional product (0.03 g, in total 0.11 g). Ananalytical sample was recrystallized twice from methanol; m.p. 188°-191°C.;

¹ H NMR (500) δ 5.38-5.36(1H, m, C₆ --H), 3.60-3.50(1H, m, C₃ --H),1.21(6H, s, C₂₆ -- and C₂₇ --H), 0.96(3H, s, C₁₉ --H), 0.58(3H, s, C₁₈--H). Mass spec. m/z 388(M⁺, 100%) 370(M⁺ --H₂ O, 90%), 355(370-CH₃,60%). Analysis: for C₂₆ H₄₄ O₂ calcd.:C, 80.35, H, 11.41; found: C,80.28, H, 11.31%. Described: M.p. 188°-190° C.; ¹ H NMR in agreementwith that described above, Pumar et al, An. Quin., Ser. C, 1988,84:105-111.

25-Hydroxy-21-norcholesterol 3-acetate (9b)

a. From the 6-methoxy derivative 8b

A solution of crude 8b (2.98 g) in acetic acid (60 ml) was stirred at70° C. for 2 h and then set aside for 16 h. Acetic acid was evaporatedon a rotary evaporator, the residue was taken in ethyl acetate (60 ml),washed with aqueous NaHCO₃ and with brine. The solvent was evaporated.The residue was dissolved in chloroform, filtered through silica gel(100 g) and crystallized from acetone to give 9b (0.90 g, 56% yield fromtosylate 7b), m. p. 128°-130° C.

¹ H NMR (500) δ 5.38(1H, br d, J=5.2 Hz, C₆ --H), 4.64-4.57(1H, m, C₆--H), 2.03(3H, s, COCH₃), 1.21(6H, s, C₂₆ -- and C₂₇ --H), 1.03(3H, s,C₁₉ --H), 0.58(3H, s, C₁₈ --H). Mass spec. m/z 370(M⁺ --CH₃ CO₂ H,100%), 352(370-H₂ O, 35%).

b. From diol 9a

A mixture of the diol (0.02 g), acetic anhydride (0.05 ml) and pyridine(0.2 ml) was set aside for 4 h. Usual workup afforded crystallineproduct (0.03 g) which was recrystallized from acetone to give materialidentical with that described under a.

3α,25-Dihydroxy-21-norcholesta-5,7-diene 3-acetate (10b)

A mixture of ene 9b (0.31 g, 0.72 mmol), powderized NaHCO₃ (0.31 g, 3.6mmol), 1,3-dibromo-5,5-dimethylhydantoin 0.14 g, 0.51 mmol) and hexane(10 ml) was stirred at the reflux temperature for 30 min. After cooling,the solid was filtered off under argon and washed with hot hexane.Combined filtrates were evaporated. To the residue xylene (10 ml) andcollidine (1 ml)were added, the mixture was heated under reflux for 1.5h, cooled and poured into water. The product was extracted with ether(3×20 ml). Combined extracts were washed consecutively with cold 5% HCl(twice), water, aqueous NaHCO₃ and brine. Bulk of the solvent wasevaporated. The residue containing the initially used xylene was dilutedwith toluene (50 ml) and ethanol (50 ml) and evaporated. The residue wasdried in high vacuum and then it was dissolved in dioxane (10 ml)containing p-toluenesulphonic acid (10 mg). The solution was stirred at55° C. for 4 h. The product (0.4 g) was recovered in the usual way andchromatographed on silica gel (15 g, hexane-ethyl acetate, 5:1).Fractions containing 5,7-diene were collected to give the title compound(0.12 g, 39% yield), m.p. 108°-110° C. (ether); λ_(max) 240, 249, 260and 272 nm;

¹ H NMR (500) δ 5.57(1H, dd, J₆,7 =5.6, J₆,4a =2.5 Hz, C₆ --H), 5.38(1H,dt, J₇,6 =5.6, J₇,9 =J₇,14 =2.7 Hz, C₆ --H), 4.71(1H, tt, J₁ =11.5, J₂=4.5 Hz, C₃ --H), 2.04(3H, s, COCH₃), 1.21(6H, s, C₂₆ -- and C₂₇ --H),0.96(3H, s, C₁₉ --H), 0.52(3H, s, C₁₈ --H). High resolution mass spec.for C₂₈ H₄₄ O₃ calcd.: 428.3290(M⁺); found: 428.3295 (20%), 368.3052(M⁺--H₃ CO₂ H, 100%).

3β,25-Dihydroxy-21-norcholesta-5,7-diene (10b)

A solution of acetate 10a (0.12 g) in ethanol (10 ml) containing 5%aqueous NaOH (0.5 ml) was set aside for 4 h and then the solvent wasevaporated in vacuo. The residue was taken in ethyl acetate (30 ml) andwashed consecutively with 5% HCl, water, saturated aqueous NaHCO₃.Evaporation of the solvent gave alcohol 10b (0.11 g) as an amorphoussolid, which was used for the next step without purification; a samplewas crystallized from toluene; m.p. 195°-198° C., λ_(max) 240, 249, 260and 272 nm.

¹ H NMR (500) δ 5.58(1H, dd, J₆,7 =5.7, J₆,4a =2.3 Hz, C₆ --H), 5.39(1H,dt, J₇,6 =5.6, J₇,9 =J₇,14 =2.8 Hz, C₆ --H), 3.70-3.60(1H, tt, J₁ =10.8,J₂ =4.5 Hz, C₃ --H), 1.21(6H, s, C₂₆ -- and C₂₇ --H), 0.95(3H, s, C₁₉--H), 0.52(3H, s, C₁₈ --H). High resolution mass spec. for C₂₆ H₄₂ O₂calcd.: 386.3185(M⁺); found: 386.3189(100%), 371.2949(M⁺ --CH₃, 20%),368.3032(M⁺ --H₂ O, 61%).

3α,25-Dihydroxy-21-nor-9,10-secocholesta-5Z,7E,10(19)-triene (11a)

A solution of diene 10a (0.11 g) in benzene-ether (2:8, 120 ml), cooledin ice-water bath was irradiated with Hanovia 608A36 medium-pressure UVlamp equipped with a Vycor filter. After 15 min (HPLC analysis indicatedover 50% conversion) the solvent was evaporated and the residue wasdissolved in ethanol (30 ml) and heated at 75° C. for 6 h. The solventwas removed and the residue was chromatographed on silica gel (12 g,hexane-ethyl acetate, 5:1) to give triene 8a (0.027 g, 24% yield) andunchanged diene 10a (0.030 g). ¹ H NMR spectrum and HPLC analysisindicated that compound 11a was over 90% pure.

¹ H NMR (400) δ 6.23(1H, d, J₆,7 =11.3 Hz, C₆ --H), 6.03(1H, d, J₇,6=11.3 Hz, C₇ --H), 5.04(1H, d, J=1.3 Hz, C₁₉ -Ha), 4.81 (1H, d, J=2 Hz,C₁₉ -Hb), 3.94(1H, tt, J₁ =7.5, J₂ =3.5 Hz, C₃ --H), 1.20(6H, s, C₂₆ --and C₂₇ --H), 0.44(3H, s, C₁₈ --H). High resolution mass spec. for C₂₆H₄₂ O₂ calcd.: 386.3185(M⁺); found: 386.3182(33%), 368.3040(M⁺ --H₂ O,6%), 353.2829(M⁺ --H₂ OCH₃, 24%).

3β,25-Dihydroxy-21-nor-9,10-secocholesta-5Z,7E,10(19)-triene 3-tosylate(11b)

A mixture of alcohol 11a (27 mg, 0.07 mmol), p-toluene-sulphonylchloride (20 mg, 0.1 mmol) and pyridine (0.25 ml) was stirred at 5° C.for 48 h and then diluted with ethylacetate (15 ml) and washed with 2%HCl, water, aqueous NaHCO₃ and brine. Evaporation of solvent gavetosylate 11b (0.025 g) as an amorphous solid, which was used for thenext step without purification. A sample was chromatographed on silicagel (1 g, hexane-ethyl acetate, 5:1);

¹ H NMR (500) δ 7.80(2H, d, J=8.3 Hz) and 7.34(2H, d, J=7.8 Hz, aromaticH), 6.10(1H, d, J₆,7 =11.3 Hz, C₆ --H), 5.10(1H, d. J₇,6 =11.4 Hz, C₇--H), 5.03(1H, d, J=1.3 Hz, C_(19a) --H), 4.82(1H, d, J=2 Hz, C₁₉ --H),4.75-4.65(1H, m, C₃ --H), 2.45(3H, s, C₆ H₄ CH₃), 1.21(6H, s, C₂₆ -- andC₂₇ --H), 0.43(3H, s, C₁₈ --H); this sample was contaminated with ca.15% of byproduct with C₁₈ H signal at δ 0.452, which was not identified.

25-Hydroxy-6ξ-methoxy-3α, 5β-cyclo-21-nor-9,10-secocholesta-7E,10(19)-diene (12a)

A mixture of rosylate lib (0.020 g), anhydrous methanol (25 ml) andpowderized NaHCO₃ (0.20 g) was set aside at 37° C. for 48 h. The solidwas filtered off and washed with ethyl acetate. Combined filtrates wereevaporated in vacuo, the residue was dissolved in ethyl acetate (20 ml)and washed with water. The solvent was removed and the crude product waschromatographed on silica gel (4.5 g. hexane-ethyl acetate, 5:1) to givethe methoxy derivative 12a (0.010 g) as a single isomer.

¹ H NMR (500) δ 5.04(1H, br s, C₁₉ -Ha), 4.99(1H, br d, J₇,6 =9.3 Hz, C₇--H), 4.88(1H, br s, C₁₉ -Hb), 4.17(1H, d, J₆,7 =9.3 Hz, C₆ --H),3.26(3H, s, OCH₃), 1.21(6H, s, C₂₆ -- and C₂₇ --H), 0.92(1H, dd, J₁=8.0, J₂ =4.6 Hz, cyclopropane H), 0.74(1H, t, J=4.5, Hz, cyclopropaneH), 0.43(3H, s, C₁₈ --H). High resolution mass spec. for C₂₇ H₄₄ O₂calcd.: 400.3341(M⁺); found: 400.3329(15%), 385.3110(M⁺ --CH₃, 3%),368.3066(M⁺ --CH₃ OH, 49%).

1α,25-Dihydroxy-6ξ-methoxy,3α,5β-cyclo-21-nor-9,10-secocholesta-7E,10(19)-diene(12b) and25-hydroxy-6ξ-methoxy-1-oxo-3α,5β-cyclo-21-nor-9,10-secocholesta-7E,10(19)-diene(12c)

The described procedure for hydroxylation of cyclovitamin was used.

A mixture of selenium dioxide (Aldrich, 99.999%, 3.62 mg, 0.033 mmol),t-butylhydroperoxide (Aldrich, 3M in 2,2,4-trimethylpentane, 56 μL,0.168 mmol) and methylene chloride (1 ml) were stirred at roomtemperature for 30 min and then pyridine (6 μL, 0.07 mmol) was added.After a few minutes diene 12a (5 mg) in methylene chloride (1 ml) wasadded. The mixture was stirred for 1 h whereupon 10% aqueous NaOH wasadded, stirring was continued for 10 min and the mixture was dilutedwith methylene chloride (10 ml). Layers were separated and the organiclayer was washed with 10% NaOH and brine. Evaporation of the solventgave a residue (7 mg) which was chromatographed on silica gel (1 g,hexane-ethyl acetate, 5:1) to give (in order of elution):

1. 1-oxo-derivative 12c (1 mg), λ_(max) =242 nm. ¹ H NMR (400) δ6.03(1H, br s, C₁₉ -Ha), 5.62(1H, br s, C₁₉ -Hb) 5.02(1H, br d, J₇,6 =9Hz, C₇ --H), 4.07(1H, d, J₆,7 =9 Hz, C₆ --H), 3.31(3H, s, OCH₃),1.21(6H, s, C₂₆ -- and C₂₇ --H), 0.95-0.85(1H, m, cyclopropane H),0.58(1H, t, J=4.5 Hz, cyclopropane H), 0.51(3H, s, C₁₈ --H); Highresolution mass spec. for C₂₇ H₄₂ O₃ calcd.: 414.3134(M⁺); found:414.3140(3%), 382.2878(M⁺ --CH₃ OH, 6%).

2. 1β-Hydroxy-derivative 12b (2 mg) which was used immediately for thenext step; ¹ H NMR (400) δ 5.24(1H, d, J=1.5 Hz, C₁₉ -HE), 5.16(1H, brs, C₁₉ -HZ), 4.95(1H, d, J₇,6 =9.3 Hz, C₇ --H), 4.30-4.20(2H, d, J₆,7=9.4 Hz overlapping a multiplet, C₆ -- and C₁ --H), 3.26(3H, s, OCH₃),1.26(6H, s, C₂₆ -- and C₂₇ --H), 0.94(1H, dd, J₁ =4.9, J₂ =8.1 Hz,cyclopropane H), 0.60(1H, t, J=4.5, Hz, cyclopropane H), 0.43(3H, s, C₁₈--H).

1α,25-Dihydroxy-21-norvitamin D₃ 1-acetate (2b) and (5E)

1α,25-Dihydroxy-21-norvitamin D₃ 1-acetate

A solution of the 3,5-cyclo derivative 12b (2 mg) in acetic acid (15 ml)was stirred at 55° C. for 20 min whereupon acetic acid was evaporated invacuo. The residue was taken in ethyl acetate (15 ml) and washed withaqueous NaHCO₃ and brine. After evaporation of the solvent a mixture ofcompounds 2b and its geometric isomer (2 mg) in a ratio ca. 2:1 (HPLC,NMR) was obtained; HLPC, 4.5% iso-propanol in hexane, retention times12.2 and 15 min, respectively.

¹ H NMR (400), isomer 2b, δ 6.34(1H, br d, J=11.2 Hz, C₆ --H), 6.02(1H,d, J₇,6 =11.2 Hz, C₇ --H), 5.34(1H, br s, C₁₉ -HE), 5.27-5.15(1H, m, C₃--H), 5.01(1H, br s, C₁₉ -HZ), 4.45-4.35(1H, m, C₁ --H), 2.03(3H, s, CH₃CO), 1.25 and 1.21(6H, 2s, C₂₆ -- and C₂₇ --H), 0.9374(1H, dd, J₁ =4.9,J₂ =8.1 Hz, cyclopropane H), 0.44(3H, s, C₁₈ --H); 5E isomer of 2b,6.57(1H, d, J=11.2 Hz, C₆ H), 5.81 (1H, d, J=11.2 Hz, C₇ --H), 5.13(1H,br s, C_(19a) --H), 4.99(1 H, br s, C_(19b) --H), 4.51-4.45(1H, br t,J=2 Hz, C₁ --H) remaining signals over imposed with those of the 5Zisomer.

1α,25-Dihydroxy-21-norvitamin D₃ (2a)

The following procedure disclosed in U.S. Pat. No. 4,555,364 forseparation of E and Z isomers was used.

The above described mixture of 2b and its 5E isomer was dissolved inethyl acetate (0.5 mil) and treated with a solution of maleic anhydride(2 mg) in ethyl acetate (0.5 ml). After 4 h (HPLC indicated completeconsumption of the E-isomer), the mixture was diluted with ethyl acetate(15 mil) and washed with saturated NaHCO₃ and brine. The solvent wasevaporated and the residue 6 mg) was dissolved in ether (1 ml) andmethanol (1 ml) and treated for 2.5 h (stirring) with powderized K₂ CO₃(50 mg). The mixture was diluted with ethyl acetate (15 ml) washed withwater and evaporated to give residue (1 mg) which was chromatographed onsilica gel (0.5 g, gradient elution hexane-ethyl acetate, 4:1 tohexane-ethyl acetate, 1:4) to give the title compound (1 mg) λ_(max) 264nm;

¹ H NMR (400) δ 6.38(1H, br d, J=11.4 Hz, C₆ --H), 6.01(1H, d, J₇,6=11.4 Hz, C₇ --H), 5.32(1H, br s, C₁₉ -H_(E)), 5.00(1H, br a, C₁₉-H_(z)), 4.47-4.40(1H, m, C₁ --H), 4.27-4.20(1H, m, C₃ --H), 1.21 (6H,s, C₂₆ -- and C₂₇ --H), 0.44(3H, s, C₁₈ --H). High resolution mass spec.for C₂₅ H₄₂ O₃ calcd.: 402.3134(M⁺ --2HO, 83%), 348.2809(M⁺ --3H₂ O,21%) ##STR6##

Biological Activity

Rats were maintained on a normal calcium and normal phosphorus diet forone week (0.47% Ca, 0.3% P), then switched to a --Ca diet for theduration of the experiment (0.02% Ca). Vitamin D compounds weresuspended in mixtures of ethanol and propylene glycol (5%:95%) and wereadministered daily for 7 days peritoneally.

After 7 days the rats were killed and the duodena were used fordetermination of intestinal calcium transport by the everted intestinalsac technique (Martin & DeLuca, 1967) and serum calcium (bone calciummobilization). The tests were made against 1,25-dihydroxyvitamin D₃ andare reported in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    INTESTINAL CALCIUM TRANSPORT AND BONE CALCIUM                                 MOBILIZING ACTIVITIES OF 21-NOR-1α,25-                                  DIHYDROXYVITAMIN D.sub.3                                                                 Amount  S/M     Serum Ca                                           Compound   (μg/day/7 day)                                                                     (Mean ± SEM)                                                                       (Means ± SEM)                                   __________________________________________________________________________    D          0       4.1 ± 0.44                                                                         4.1 ± 0.23                                      1.25-(OH).sub.2 D.sub.3                                                                  1.0     7.9 ± 0.33                                                                         5.3 ± 0.10                                      21-nor-1,25-(OH).sub.2 D.sub.3                                                           0.1     7.9 ± 0.82                                                                         4.5 ± 0.1                                                  1.0     8.0 ± 0.65                                                                         4.5 ± .09                                       __________________________________________________________________________

The results show that the 21-nor-1,25-dihydroxyvitamin D compound isless active than 1,25-dihydroxyvitamin D₃ in both mobilization ofcalcium from bone and intestinal calcium transport. However, the21-nor-1,25-dihydroxyvitamin D₃ compound has highly significantintestinal calcium transport activity. The amount of bone calciummobilizing activity is considerably less than 1,25-dihydroxyvitamin D₃.These compounds therefore, by showing preferential activity onintestinal calcium transport and reduced calcium mobilizing activity inbone suggest that they are preferred agents for the treatment of adisease where bone loss is a major issue, such as osteoporosis,osteomalacia and renal osteodystrophy.

For treatment purposes, the novel compounds of this invention may beformulated for pharmaceutical applications as a solution in innocuoussolvents, or as an emulsion, suspension or dispersion in suitablesolvents or carriers, or as pills, tablets or capsules together withsolid carriers, according to conventional methods known in the art. Anysuch formulations may also contain other pharmaceutically-acceptable andnon-toxic excipients such as stabilizers, anti-oxidants, binders,coloring agents or emulsifying or taste-modifying agents.

The compounds may be administered orally, parenterally or transdermally.The compounds are advantageously administered by injection or byintravenous infusion of suitable sterile solutions, or in the form ofliquid or solid doses via the alimentary canal, or in the form ofcreams, ointments, patches, or similar vehicles suitable for transdermalapplications. Doses of from 0.5 μg to 50 μg per day of the compounds areappropriate for treatment purposes, such doses being adjusted accordingto the disease to be treated, its severity and the response of thesubject, as is well understood in the art. Since the new compoundsexhibit specificity of action, each may be suitably administered alone,in situations where only calcium transport stimulation is desired, ortogether with graded doses of another active vitamin D compound--e.g.1α-hydroxyvitamin D₂ or D₃, or 1α,25-dihydroxyvitamin D₃ --in situationswhere some degree of bone mineral mobilization (together with calciumtransport stimulation) is found to be advantageous.

We claim:
 1. A compound having the formula ##STR7## where X₆ may behydrogen or a hydroxy-protecting group, and Z is selected from the groupconsisting of Y, --OY, --CH₂ OY, --C═CY and --C═CHY, where the doublebond may have the cis or trans stereochemical configuration, and where Yis selected from the group consisting of hydrogen, methyl, --CR⁵ O and aradical of the structure, ##STR8## where m and n independently representintegers from 0 to 5, where R¹ is selected from the group consisting ofhydrogen, hydroxy, protected-hydroxy, fluoro, trifluoromethyl, and C₁₋₅alkyl, which may be straight-chain or branched and optionally bear ahydroxy or protected-hydroxy substituent, and where each of R², R³, andR⁴ independently is selected from the group consisting of hydrogen,fluoro, trifluoromethyl, and C₁₋₅ alkyl, which may be straight-chain orbranched and optionally bear a hydroxy or protected-hydroxy substituent,and where R¹ and R², taken together, represent an oxo group, or analkylidene group, ═CR² R³ or the group --(CH₂)p--, where p is an integerfrom 2 to 5, and where R³ and R⁴, taken together, represent an oxogroup, or the group --(CH₂)q, where q is an integer from 2 to 5, andwhere R⁵ represents hydrogen, hydroxy, protected hydroxy, or C₁₋₅ alkyl.2. The compound of claim 1 where Z is CH₂ CH₂ CH₂ C(CH₃)₂ OH and X₆ ishydrogen.
 3. A pharmaceutical composition containing at least onecompound as claimed in claim 1 together with a pharmaceuticallyacceptable excipient.
 4. The pharmaceutical composition of claim 3containing 21-nor-1α,25-dihydroxyvitamin D₃ in an amount from about 0.5μg to about 50 μg.
 5. A compound having the formula ##STR9## where X₄and X₅, which may be the same or different are hydrogen, hydroxy, ortaken together to form an oxo group, and Z is as defined in claim 1.